Bend over backward

to force (an object, especially a long or thin one) from a straight form into a curved or angular one, or from a curved or angular form into some different form:
to bend an iron rod into a hoop.
to direct or turn in a particular direction:
to bend one’s energies to the task.
to cause to submit or yield:
to bend someone to one’s will.
to modify or relax (restrictions, regulations, etc.) temporarily or in certain circ-mstances:
to bend the rules.
to incline mentally (usually followed by to or toward):
bending his thoughts back toward his childhood.
to pull back the string of (a bow or the like) in preparation for shooting.
nautical. to fasten.
archaic. to strain or brace tensely (often followed by up).
to become curved, crooked, or bent:
a bow that bends easily.
to -ssume a bent posture; stoop (often followed by over):
to bend as one walks; to bend over and pick up something.
to turn or incline in a particular direction; be directed:
the road bent toward the south.
to yield or submit; give in.
to bow in submission or reverence:
bending to one’s monarch.
to direct one’s energies:
we bent to our work as the bell sounded.
the act of bending.
something that bends; curve; crook:
a bend in the road; a bend in the curtain rod.
nautical. any of various loops or knots for joining the ends of two ropes or the like, or for joining the end of a rope or the like to some other object.
bends, nautical.

thick planking immediately below the waterways of a wooden vessel.
the wales of a vessel.

the bends, aeroembolism (def 2).
around / round the bend, slang. insane; crazy:
these interruptions will send me round the bend!
bend / lean / fall over backward, to exert oneself to the utmost; make a serious effort:
they bent over backward to make sure their guests were comfortable.
historical examples

the highgrader william macleod raine

verb bends, bending, bent
to form or cause to form a curve, as by pushing or pulling
to turn or cause to turn from a particular direction: the road bends left past the church
(intransitive; often foll by down, etc) to incline the body; stoop; bow
to submit or cause to submit: to bend before superior force
(transitive) to turn or direct (one’s eyes, steps, attention, etc)
(transitive) to concentrate (the mind); apply oneself closely
(transitive) (nautical) to attach or fasten, as a sail to a boom or a line to a cleat
(informal) bend over backwards, to make a special effort, esp in order to please: he bends over backwards to accommodate his customers
(informal) bend someone’s ear, to speak at length to an unwilling listener, esp to voice one’s troubles
(informal) bend the rules, to ignore rules or change them to suit one’s own convenience
noun
a curved part, as in a road or river
(nautical) a knot or eye in a line for joining it to another or to an object
the act or state of bending
(brit, slang) round the bend, mad; crazy; eccentric
noun
(heraldry) an ordinary consisting of a diagonal line traversing a shield
v.
n.

bend one’s elbow
bend over backwards
bend someone’s ear